וַיְהִ֣י ׀ בַּעֲל֣וֹת הַמִּנְחָ֗ה וַיִּגַּ֞שׁ אֵלִיָּ֣הוּ הַנָּבִיא֮ וַיֹּאמַר֒ יְהוָ֗ה אֱלֹהֵי֙ אַבְרָהָם֙ יִצְחָ֣ק וְיִשְׂרָאֵ֔ל הַיּ֣וֹם יִוָּדַ֗ע כִּֽי־אַתָּ֧ה אֱלֹהִ֛ים בְּיִשְׂרָאֵ֖ל וַאֲנִ֣י עַבְדֶּ֑ךָ ובדבריך [וּבִדְבָרְךָ֣] עָשִׂ֔יתִי אֵ֥ת כָּל־הַדְּבָרִ֖ים הָאֵֽלֶּה׃
Um die Zeit, da das Speiseopfer dargebracht wird, trat der Prophet Elija hin und sprach: Herr, Gott Abrahams, Isaaks und Israels, heute werde kund, dass du Gott bist in Israel, und dass ich dein Knecht bin, und dass auf dein Wort ich all diese Dinge getan habe.
Rashi
And at Your word have I done. That I sacrificed on a private altar during the period of the prohibition of [offering sacrifices on] private altars.19This verse implies that God commanded Eliyahu to offer the sacrifice on Mount Carmel even though private altars were not permitted once the Beis Hamikdosh had been built. See footnote on v. 30 above and Tosafos in Maseches Sanhedrin 89b.